Trim control device for boats



March 5, 1968 Q w. M. JOY 3,371,642

TR IM CONTROL DEVICBFOR BOATS Filed Oct. 15, 1965 3 Sheets-Sheet 1 A///?/J K j'/;/

INVENTOR.

M77??? 2% Ja w. M. JOY

TRIM CONTROL DEVICE FOR BOATS March 5, 1968 Filed on. 15, 1965 3Sheets-Sheet 2 March 5, 1968 Filed Oct. 15, 1965 W. M. JOY

TRIM CONTROL DEVICE FOR BOATS 5 Sheets-Sheet I5 INVENTOR.

United States Patent 3,371,642 TRIM CONTROL DEVICE FOR BOATS William M.Joy, 1615 N. River Road, St. Clair, Mich. 48079 Filed Oct. 15, 1965,Ser. No. 496,553 8 Claims. (01. 114-665) This invention relatesgenerally to improvements in boat trimming stabilizers and, moreparticularly, to a new and improved boat stabilizer which is adapted tobe attached or mounted on the stern of a boat and be selectivelypositioned for coaction with the water during forward movement of theboat to control the longitudinal attitude of the boat.

The attitude, stability and movement of a boat during its propulsionthrough the water is affected by various factors, such as the shape ofthe hull, the area and symmetry and surface of the hull which is incontact with the water and the draft or depth to which the boat extendsbeneath the surface of the water. The operation of boats may also begreatly affected by the amount of power which is used to propel themsuch that a boat which is designed to operate satisfactorily with amotor of one particular size will assume one attitude in the water underoptimum operating conditions; however, the operational efficiency ofthis same boat will be greatly reduced when the boat is provided with amotor of increased power due to the boat assuming a much greaterattitude in the water.

There has heretofore been proposed various methods of overcoming theabove stability problems whereby a particular boat may be eflicientlyoperated with motors of varying power capacities. One very popularmethod of over-coming these problems is by providing one or morerearwardly extending plates or brackets on the stern of the boat whichform extensions on the bottom surface area thereof, these plates orbrackets being arranged at a preselected position relative to the bottomand transom of the boat for coaction with the water, whereby the boatwill move through the water at a proper attitude under particularloading and power conditions. It will be noted, however, that suchheretofore commonly employed devices have the inherent disadvantage thatthey only operate efficiently under particular loading conditions, i.e.,certain fuel and passenger loads. More recently, devices have beenproposed which are capable of being adjustable to accommodate variousloading conditions but such devices heretofore known and used have beenrelatively complex in operation and construction and are accordinglydifiicult to install and operate, along with being relatively expensiveto commercially produce.

It is accordingly a general object of the present invention to provide anew and improved stabilizing device of the above character which isextremely simple in construction and operation and which may be readilyadjusted to accommodate various loading conditions to which a particularboat may be subjected.

It is a more particular object of the present invention to provide a newand improved boat trimming device of the above character which may bereadily adjusted to accommodate relatively heavy or light bow loading ofthe boat.

It is another object of the present invention to provide a new andimproved boat trimming device of the above character which obviates thenecessity of providing relatively complex support brackets and the likeon the bottom or transom of a boat for the support of the trimmingdevice.

It is still another object of the present invention to provide a new andimproved boat trimming apparatus of the above character that is adaptedto be used on marine hydrofoil systems.

Patented Mar. 5, 1968 It is yet another object of the present inventionto provide a new and improved boat trimming device of the abovecharacter which is of an extremely simple design, rugged construction,is easy to assemble and economical to commercially produce. Y Otherobjects and advantages of the present invention will become apparentfrom the following detailed description taken in conjunction with theaccompanying drawings, wherein:

FIGURE 1 is a top elevational view of the boat trimming apparatus of thepresent invention, as shown operatively installed on a conventionalmotor boat or the like;

FIGURE 2 is an elevated perspective view of the stern portion of theboat illustrated in FIGURE 1;

FIGURE 3 is a fragmentary side elevational view of the boat trimmingapparatus illustrated in FIGURE 1;

FIGURE 4 is an enlarged fragmentary cross-sectional view of thestructure illustrated in FIGURE 3;

FIGURE 5 is a fragmentary cross-sectional view taken along the line 5-5of FIGURE 4;

FIGURE 6 is an enlarged fragmentary side elevational view of the boattrimming apparatus of the present invention;

FIGURE 7 is a fragmentary cross-sectional view taken along the line 7-7of FIGURE 6;

FIGURE 8 is an elevated perspective view of a slightly modifiedembodiment of the boat trimming apparatus of the present invention, asshown operatively installed on a marine hydrofoil system;

FIGURE 9 is an enlarged side elevational view of a portion of thestructure illustrated in FIGURE 8, as seen in the direction of the arrow9 thereof;

FIGURE 10 is a bottom elevational view of a portion of the structureillustrated in FIGURE 8, as seen in the direction of the arrow 10thereof;

FIGURE 11 is a side elevational view of another embodiment of the boattrimming apparatus of the present invention; and

FIGURE 12 is a side elevational view of the structure illustrated inFIGURE 11, as seen in the direction of the arrow 12 thereof.

Referring now to FIGURES 1 through 3 of the drawings, the boat trimmingapparatus of the present invention, generally designated by the numeral10, is shown in operative association with a boat 12 of conventionalconstruction, such as an outboard motor boat of the pleasure or racingtype having a transom 14 at its stern to which a portable outboard motor(not shown) of the usual kind may be conveniently attached. The boattrimming apparatus 10 of the present invention comprises a pair ofidentical trim assemblies, generally designated by the numeral 16, whichare adapted to be mounted on the port and starboard sides of the transom14 and extend rearwardly therefrom to provide portions of considerablearea extending rearwardly or aft of the bottom of the boat 12 and in thegeneral plane thereof, whereby to resist lateral and longitudinaltilting of the boat as the same is propelled through the water undervarious operating and loading conditions. It may be noted that, togetherwith the above described method of securing the forward portions 20 ofthe trim tab elements 18 to the boat bottom 25, it may be possible tobend the elements 18 approximately parallel to their transverse axes,whereby the elements 18 will be generally L-shaped. The upwardlyprojecting portions of the elements 18 defined by these bends may thenbe rigidly secured to the outer surface of the boat transom 14 in amanner such that the rear portions 26 of the tabs 18 project rearwardlyor aft of the transom 14 in substantial coplanar relation with the boatbottom 25.

As best seen in FIGURES 1, 2 and 6, each of the trim assemblies 16comprises a flat or planar plate-like element or trim tab 18 which isgenerally rectangular in shape and is preferably constructed ofstainless steel or a similar strong, corrosion-resistant material. Thetrim tabs 18 are preferably of uniform thickness which is selected suchthat the tabs 18 are somewhat flexible about their transverse or lateralaxes, as will be described. The trim tab 18 of both of the assemblies 16is adapted to be mounted on the boat 12 by having the forward portionthereof, herein designated 20, rigidly secured by means of a pluralityof countersunk screws, bolts or the like 22 to the exterior surface 24of the bottom 25 of the boat 12, whereby the rear portions, hereindesignated 26, of each of the tabs 18 projects aft of the boat transom14 and in substantial coplanar relation with the bottom of the boat 12,as best seen in FIGURE 6. By virtue of the flexible construction of thetrim tabs 18, the rear portions 26 thereof are adapted to pivot or flexangularly upwardly and downwardly relative to the forward portions 20thereof and thus relative to the plane of the bottom of the boat 12. Bythus angularly raising or lowering the rear portions 26 of the trim tabs18, the tabs 18 will serve to minimize both longitudinal and lateraltilting of the boat 12 such that the same may be propelled through thewater at a desirable attitude under various operational and loadingconditions, as will later be described.

Referring now to FIGURES 3, 4, 5 and 7, each of the trim assemblies 16comprises an actuating mechanism 28 for independently raising andlowering the rear portions 26 of the associated trim tab 18 and thus forcontrolling the stability of the boat 12. As best seen in FIGURE 4, eachof the mechanisms 28 comprises a reversible electric motor 30 ofconventional design which is adapted to be actuated by electrical energyfrom any suitable source, such as batteries or an outboard motor poweredgenerator or the like. The motor 30 of each mechanism 28 is adapted tobe supported on the interior side of the boat transom 14 by an L-shapedmounting bracket 32 which has a downwardly extending leg section 34secured to the transom 14 by suitable screws, bolts or the like 36, andan upper leg section 38 that is secured to the lower side of the motor30 by suitable screws or bolts 40. The motors 30 may be housed withinsuitable covers 41 which are secured at their lower ends to the brackets32 by suitable screws 42. The motors 30 of each of the trim assemblies16' have a drive shaft 43 which is connected to a right angle drive unit44 that is secured to the top of the associated motor 30 by suitablescrews or bolts 46. The right angle drive units 44 include externallythreaded output shafts 48 which, upon actuation of the motors 30, areadapted to move internally threaded shafts 50 that are threadablymounted upon the output shafts 48 in directions axially orlongitudinally thereof. As seen in FIGURE 4, the shafts 50 extendthrough openings 52 in the upper end of the transom 14 and throughcentral bores 54 formed in a pair of sealing collars 56 that are securedto the exterior side of the transom 14 coaxially of the openings 52 bysuitable screws 58. Suitable O-ring sealing members or the like 60 areretained within semi-circular shaped grooves 62 formed around the bores54 of the collars 56, the sealing members 60 serving to prevent anywater from entering into the boat 12 between the outer periphery of theshaft 50 and the inner periphery of the openings 52.

The outer ends of the shafts 50 are formed with generally rectangularshaped end sections 64 which are adapted to be pivotably connectedwithin bifurcated or yoke-shaped end sections 66 that are formed on theupper ends of a pair of actuating rods 68 by suitable pivot pins or thelike 70. As seen in FIGURE 5, the pins 70 may be retained withinsuitable axially aligned bores 72 and 74 that are formed in the endsections 64 and 66, respectively, by conventional cotter keys or thelike 76.

Referring now to FIGURE 7, the lower ends of the actuating rods 68 areformed with rectangular shaped end sections 78 which are adapted to bepivot-ably secured between a pair of spaced parallel bosses and 82 thatare secured to the tops of the rearmost portions of the end sections 26of each of the trim tabs 18 as by welding or the like, the end sections78 being pivotably connected to the bosses 80 and 82 by suitable pivotpins or the like 84 which extend through axially aligned bores 86 and 88formed in the end section 78 and bosses 80, 82, respectively. The pins84 may be retained within the bores 86 and 88 by suitable cotter keys89.

The dimension of the shafts 50 and actuating rods 68 of each of the trimassemblies 16 are selected such that as the shafts 50 move axially awayfrom the exterior surface of the transom 14, upon appropriateenergization of the associated motors 30, the rods 68 will be biasedupwardly and outwardly, as indicated by the phantom lines in FIG- URE 3,resulting in the rear end portions 26 of the trim tabs 18 being flexedupwardly relative to the plane of the bottom of the boat 12. In asimilar manner, as the shafts 50 move axially in a direction toward theinterior surface of the transom 14, the associated rods 68 will bebiased downwardly, resulting in the rear end portions 26 of the trimtabs 18 being biased downwardly relative to the plane of the bottom ofthe boat 12, as also indicated by the phantom lines in FIGURE 3.

In operation of the boat stabilizing apparatus 10 of the presentinvention, assuming that the boat 12 is being initially propelled oraccelerated, for example, when moving away from a dock or similarmooring structure, the bow of the boat 12 will tend to rise out of thewater. At such time as any appreciable amount of waves are encountered,the boat will be subjected to substantial bouncing and pounding,resulting in unpleasant jarring of the boat 12 and its occupants. Toovercome such unpleasant effects resulting from the improper attitude ofthe boat 12 moving through the water, the electric motors 30 of each ofthe trim assemblies 16 may be appropriately energized such that theshafts 50 are biased inwardly or toward the interior surface of thetransom 14 resulting in the rear end portions 26 of the trim tabs 18being biased or flexed downwardly relative to the plane of the bottom ofthe boat 12. As the end portions 26 are thus moved, the hydrodynamiceffect of the water impinging against the lower surfaces of the portions26 will tend to raise the stern of the boat 12 sufficient to attain aproper attitude and thus obviate the aforementioned bouncing andpounding of the boat 12 and unpleasant effects resulting therefrom.

When the load distribution in the boat 12 is such that the bow or frontend thereof rides lower in the water than the stern or rear end of theboat, the motors 30 of each of the trim assemblies 16 may be energizedsuch that the shafts 50 are biased outwardly or away from the outersurface of the transom 14, resulting in the rear end portions 26 of thetrim tabs 18 being biased or flexed upwardly relative to the plane ofthe bottom of the boat 12. The hydrodynamic effect of the water on theend portions 26 disposed in their raised positions will cause the sternof the boat 12 to be lowered in the water as the boat 12 is propelled,whereby the boat 12 will attain a desirable horizontal attitude.

It may be noted that by virtue of the fact that each of the trimassemblies 16 is independently operable, it may be possible to raise therear end portion 26 of one of the trim tabs 18 and simultaneously lowerthe rear end portion 26 of the other of the trim tabs 18, whereby toachieve lateral stabilizing of the boat 12 under various loading andoperating conditions and thus prevent the boat from tilting toward oneside or the other as the same is propelled through the water.

It will thus be seen that the boat stabilizing apparatus 10 of thepresent invention provides means for controlling both the longitudinaland lateral stability of a boat in the water, which apparatus, ashereinabove described, may be installed in a minimum amount of time andbe controlled by relatively simple manipulation of any suitable controlsuch as electrically operated switches or the like for appropriatelyenergizing the motors 30 of the trim assemblies 16.

Referring now to FIGURES 8 through 10, a slightly modified constructionof the boat trimming apparatus of the present invention is shown inoperative association with a boat 100 of conventional constructionincluding port and starboard sides 102 and 104, respectively, and abottom section 106. The boat 100 is provided with forwardly andrearwardly positioned hydrofoils 108 and 110, respectively, which aredisposed below the bottom section 106 of the boat 100 and extendtransversely of the longitudinal axis thereof. The forward hydrofoil 108is attached to the bottom section 106 by a plurality of substantiallyvertical struts 112, 114 and 116. In a similar manner, the rearhydrofoil 110 is secured to the bottom section 106 of the boat 100 by apair of laterally spaced struts 118 and 120.

In accordance with the principles of the present invention, the forwardhydrofoil 108 is provided with a pair of laterally spaced plate-likeelements or trim tabs 122 which are preferably of the same generalconstruction as the trim tabs 18 hereinabove described. It may be notedthat during most loading and operating conditions, it is not necessaryto provide the rear hydrofoil 110 with the trim tabs 122 since the rearhydrofoil 110 tends to seek the same level of submersion as the fronthydrofoil 108 to maintain the boat 100 at a substantially level keel;however, it will be apparent that the rear hydrofoil 110 may be providedwith such trim tabs when the design of the boat and the operatingconditions therefor so warrant.

As best seenin FIGURE 9, each of the trim tab members 122 comprises aforward portion 124 which is adapted to be secured to the lowermost sideof the hydrofoil 108 by means of suitable screws, bolts or the like 126,whereby the rear portions 128 of the trim tabs 122 project toward therear end of the boat 100 in substantial coplanar relation with thebottom surface of the hydrofoil 108. By virtue of the flexibleconstruction of the trim tabs 128, is hereinabove described, the rearportions 128 are adapted to pivot or flex angularly upwardly anddownwardly relative to the forward portions 124 thereof and thusrelative to the plane of the lower surface of the hydrofoil 108. By thusvarying the angular relation of the rear portions 128 of the trim tabs122 relative to the plane of the lower surface of the hydrofoil 108, theboat operator may control the attitude of the boat 100 as the same ispropelled through the water, and may also maintain the hull of the boat100 at a predetermined distance above the surface of the water.

Means for thus biasing the rear portions 128 of the trim tabs 122angularly upwardly and downwardly is provided by a pair of actuatingshafts 130 which extend upwardly from the rear portions 128 of the trim.tabs 122 and are secured at their lower ends to the upper surfaces ofthe portions 128 by means of suitable pairs of bosses 132 and pivot pins134 that are substantially identical in construction and operation tothe bosses 80 and pivot pins 84 hereinbefore described in connectionwith the trim tab 18 and shafts 68.

The upper ends of the shafts 130 extend through suitable openings 136 inthe bottom section 106 of the boat 100 and are connected to suitableactuating mechanisms (not shown) adapted to selectively bias the shafts130 axially upwardly or downwardly, whereby to pivot the rear portions128 of the trim tabs 122 upwardly or downwardly, as above described. Onesuitable mechanism for selectively biasing the shafts 130 is thehereinbefore described actuating mechanism 28 which includes a suitableelectric motor 30, drive unit 44 and externally threaded shaft 148.Suitable sealing means (not shown) such as O-rings or the like arepreferably interposed between the outer periphery of the shafts 130 andthe inner periphery of the openings 136 to prevent water from passingbetween these surfaces into the interior of the boat 100.

Referring now to FIGURE 10, the rear portions 128 of each of the trimtab members 122 are provided with generally rectangular shaped flaps ortabs 140 which are adapted to have their forward end portions secured asby spot-welding, screws, bolts or the like to the lower surface of therear portions 128, the rear portions of the flaps or tabs 140 extendingrearwardly of the trim tabs 122 and being adapted to be manually bentupwardly or downwardly in accordance with the operating conditions towhich the boat is to be subjected. More particularly, the rear ends ofthe flaps are adapted to be bent upwardly or downwardly to compensatefor drag, motor size and various other parameters.

Referring now to FIGURES 11 and 12, a slightly modified embodiment ofthe boat trim apparatus illustrated in FIGURES 8 through 10 is shown inoperative association with a boat of conventional design and comprisinga hull portion 152 which terminates at its stern end in a substantiallyvertical transom section 154. In accordance with the principles of thepresent invention, the boat 150 is provided with a trim tab support bar156 which extends transversely of the bottom 158 of the hull 152slightly forward of the transom 154. The bar 156 is supported at aposition spaced from and substantially parallel to the bottom 158 by apair of laterally spaced, generally U- shaped support brackets 160 whichare secured at their upper ends by suitable screws, bolts or the like(not shown) to the boat bottom 158, the opposite ends of the bar 156being fixedly secured within the lower ends of the brackets 160, as bestseen in FIGURE 11.

The bar 156 is adapted to support a pair of laterally spaced trim tabmembers 162 which are substantially identical in construction andoperation to the hereinbefore described trim tabs 122 and 18. As bestseen in FIGURE 11, the forward portions of the trim tabs 162 are securedby suitable screws, bolts or the like (not shown) to the lower side ofthe bar 156, the rear portions of the trim tabs 162 extending rearwardlyof the bar 156 at positions spaced from and substantially parallel tothe bottom section 158 of the boat hull 152. In a preferred constructionof the present invention, the rear ends of the trim tabs 162 preferablyterminate slightly forward of the plane of the boat transom 154. Therear portions, herein designated 166, of the trim tab members 162 areadapted to pivot or flex angularly upwardly and downwardly relative tothe plane of the forward portions thereof, as described in connectionwith the trim tabs 18 and 122, whereby to control the longitudinaltilting of the boat 150 such that the same may be propelled through thewater at a desirable attitude under various operational and loadingconditions, as above described.

Means for thus angularly raising or lowering the rear portions 166 ofthe trim tabs 162 is provided by suitable actuating shafts 168 that areattached to the upper surfaces of the portions 162 in the abovedescribed manner and which extend through suitable openings (not shown)in the bottom section 158 of the boat 150, these shafts beingoperatively connected to suitable actuating mech anisms (not shown) forselectively biasing the same axially upwardly or downwardly, as washereinbefore described.

While it will be apparent that the preferred embodi ments hereinillustrated are well calculated to fulfill the objects above stated, itwill be appreciated that the present invention is susceptible tomodification, variation and change without departing from the properscope or fair meaning of the subjoined claims.

What is claimed is:

1. In an apparatus for stabilizing a boat having a hull which terminatesat its stern end in an upwardly extending transom section,

a pair of flat rectangular shaped trim tab elements constructed of arelatively flexible material and having a first portion secured to theunderside of the hull at the opposite ends of the transom section and a7 second portion extending rearwardly of the transom section anddisposed in substantially coplanar relation with the underside of thehull,

a pair of actuating motors mounted on said transom section,

a pair of shafts aligned with said trim tab elements and extendingthrough laterally spaced openings in said transom section,

drive means connected to said motors and adapted to move said shaftsalong the longitudinal axes thereof, and

a pair of actuating rods pivotably connected at their upper ends to saidshafts and at their lower ends to the upper sides of said secondportions of said trim tab elements,

energization of said motors being adapted to move said shaftslongitudinally thereof whereby to vary the inclination of said secondportions of said trim tab elements relative to the plane of theunderside of the hull.

2. The invention as set forth in claim 1 wherein said trim tab elementsare constructed of stainless steel.

3. The invention as set forth in claim 1 wherein said drive units arethreadably connected to said shafts.

4. In a boat stabilizing apparatus,

means defining a substantially fiat elongated trim tab element having afirst sect-ion rigidly secured to a portion of the underside of the boatwhich is in contact with the water as it is propelled through the waterand a second section integral with said first section and extendingrearwardly of said first section and disposed in substantial coplanarrelation with said portion of the boat, and

means for varying the inclination of said second section of said trimtab element relative to said first section thereof including first shaftmeans pivotably connected at the lower end thereof to said secondsection and second shaft means pivotably connected to the upper end ofsaid first shaft means and motor means for longitudinally biasing one ofsaid shaft means.

5. In combination with a marine craft having a hydrofoil system,

means defining a substantially fiat elongated trim tab element having afirst portion rigidly secured to the hydrofoil and a second portionextending rearwardly of the hydrofoil and disposed in substantialcoplanar relation with said first portion, and

means for varying the inclination of said second portion of said trimtab element relative to the hydrofoil including first shaft meanspivotably connected at the lower end thereof to said second section andsecond shaft means pivotably connected to the upper end of said firstshaft means and motor means for longitudinally biasing one of said shaftmeans.

6. In an apparatus for stabilizing a boat having a hull which terminatesat its stern end in an upwardly extending transom section,

a pair of flat rectangular shaped trim tab elements constructed of arelative flexible material and each having first and second portions,

a trim tab support bar extending laterally of the hull at a positionspaced slightly below the underside thereof,

means including support bracket means for supporting said bar at saidposition spaced below the underside of the hull,

means for rigidly securing said first portions of said trim tab elementsto said bar in a manner such that said second portions thereof extendrearwardly toward said transom below and substantially parallel to theunderside of the hull, and

means pivotably connected directly to the upper sides of said secondportions and including shaft means extending upwardly through the hullfor varying the inclination of said second portions of said trim tabelements relative to the plane of the underside of the hull.

7. In a boat stabilizing apparatus,

a pair of trim tab elements constructed of a relatively flexiblematerial and having first portions rigidly secured to the stern end ofthe boat and second portions extending rearwardly of the boat anddisposed in substantial coplanar relation with the underside thereof;

means for independently varying the inclination of said second portionsof said trim tab elements relative to the plane of the underside of theboat, said last mentioned means comprising first shaft means pivotablyconnected to said second portions of said elements, said second shaftmeans movably connected to said first shaft means, and power means foraxially moving said second shaft means.

8. A stabilizing device for a boat having a bottom section and a transomsection extending upwardly from said bottom section, said deviceincluding,

a trim tab element comprising an elongated, uniformly thick, relativelyflexible member having a first por-' tion rigidly secured to one of saidboat sections and a second portion extending rearwardly of the transomsection in substantial coplanar relation with the bottom section,

an actuating element secured to said second portion of said memberadjacent the rear end thereof and operable to bend said second portionboth upwardly and downwardly relative to the plane of the bottomsection,

upward bending movement of said member being operable to create adownward force on the stern of the boat during forward movement thereofwhereby the bow of the boat will be raised, and downward bendingmovement of said member being operable to create an upward force on thestern of the boat during forward movement thereof whereby the bow of theboat will be lowered.

References Cited UNITED STATES PATENTS 1,237,7'15 8/1917 Smith 1l4-66.53,111,103 11/1963 Bennett 11466.5 3,120,829 2/1964 Chew et a1. 114-65.SX 3,208,422 9/ 1965 Schopmeyer 11466.5

ANDREW H. FARREIJL, Primary Examiner.

1. IN AN APPARATUS FOR STABILIZING A BOAT HAVING A HULL WHICH TERMINATESAT ITS STERN END IN AN UPWARDLY EXTENDING TRANSOM SECTION, A PAIR OFFLAT RECTANGULAR SHAPED TRIM TAB ELEMENTS CONSTRUCTED OF A RELATIVELYFLEXIBLE MATERIAL AND HAVING A FIRST PORTION SECURED TO THE UNDERSIDE OFTHE HULL AT THE OPPOSITE ENDS OF THE TRANSOM SECTION AND A SECONDPORTION EXTENDING REARWARDLY OF THE TRANSOM SECTION AND DISPOSED INSUBSTANTIALLY COPLANAR RELATION WITH THE UNDERSIDE OF THE HULL, A PAIROF ACTUATING MOTORS MOUNTED ON SAID TRANSOM SECTION, A PAIR OF SHAFTSALIGNED WITH SAID TRIM TAB ELEMENTS AND EXTENDING THROUGH LATERALLYSPACED OPENINGS IN SAID TRANSOM SECTION, DRIVE MEANS CONNECTED TO SAIDMOTORS AND ADAPTED TO MOVE SAID SHAFTS ALONG THE LONGITUDINAL AXESTHEREOF, AND